The present invention relates to a process cartridge detachably mountable to a main assembly of the electrophotographic image forming apparatus, a load producing member and an electrophotographic image forming apparatus.
Here, the electrophotographic image forming apparatus is an apparatus which forms images on recording materials through an electrophotographic image forming process. For example, it includes an electrophotographic copying machine, an electrophotographic printer (LED printer, laser beam printer or the like), an electrophotographic printer type facsimile machine, an electrophotographic printer type word processor and the like.
The process cartridge is a cartridge comprising as a unit at least one of process means such as charging means, developing means and cleaning means, and an electrophotographic photosensitive drum, the cartridge being detachably mountable to a main assembly of the electrophotographic image forming apparatus. The process means at least one of the charging means for electrically charging the photosensitive drum, developing means for developing an electrostatic latent image formed on the photosensitive drum, and cleaning means for removing a developer remaining on the photosensitive drum.
Heretofore, a process cartridge type is used, in which a cartridge comprising as a unit the electrophotographic photosensitive drum and at least one of the charging means, the developing means and the cleaning means, the cartridge being detachably mountable to the main assembly of the electrophotographic image forming apparatus.
The process cartridge type is advantageous because the maintenance operations for the process means can be, in effect, carried out by the user. Therefore, the operativity is significantly improved, and for this reason, the process cartridge type is widely used in the field of the electrophotographic image forming apparatus.
Recently, the demand for color electrophotographic image forming apparatus capable of forming color images increases.
In order to form high quality color images at high-speed with high operativity, a tandem type is used in which the photosensitive drums of the image formation stations for image formations in yellow Y, magenta M, cyan C and black K images, are juxtaposed with each other.
With this structure, the four color image formations are carried out independently to form a single color image. The positions of the image formed by the photosensitive drums may be deviated from the target (ideal) positions. In the following descriptions, the relative positional deviation among the different colors due to positional deviation from the target positions is called xe2x80x9ccolor misregistrationxe2x80x9d.
In the tandem type image forming apparatus, minimizing the color misregistration leads to image quality color image, and therefore, various measurements are taken.
For example, the positions of the image forming points for the respective colors are measured, and the positions are corrected; a rotary encoder is provided on the drum driving shaft to detect the rotation variation of the photosensitive drum, and control the driving motor in accordance with the detection so as to suppress the rotation variation.
As described hereinbefore, a plurality of process means in the form of a rotary member are provided around the photosensitive drum. In the case that peripheral speed of a rotatable member contacted to the photosensitive drum is higher than that of the photosensitive drum, the rotational speed of the photosensitive drum is unstable because the photosensitive drum is driven by the rotary member. In addition, if there is a member which is contacted to the photosensitive drum and which moves in the axial direction, the position, in the axial direction, of the photosensitive drum is unstable. Because of these factors, there is a liability that color misregistration results. Therefore, it is desired to provide means cable of suppressing the misregistration.
Accordingly, it is a principal object of the present invention to provide a process cartridge, a load producing member and an electrophotographic image forming apparatus with which the electrophotographic photosensitive drum can be stably rotated.
It is another object of the present invention to provide a process cartridge, a load producing member and an electrophotographic image forming apparatus with which the photosensitive drum can be rotated at a constant rotational speed even when the electrophotographic photosensitive drum is subjected to an external force.
It is a further object of the present invention to provide a process cartridge, a load producing member and an electrophotographic image forming apparatus with which the position, in the axial direction, of the photosensitive drum. It is a further object of the present invention to provide a process cartridge, a load producing member and an electrophotographic image forming apparatus with which color misregistration in color image formation can be suppressed.
It is a further object of the present invention to provide a process cartridge, a load producing member and an electrophotographic image forming apparatus with which the rotation and position of the photosensitive drum are stabilized so as to produce high-quality color images giving the electrophotographic photosensitive drum is subjected to an external force.
Here, the external force which might be imparted to the photosensitive drum may be produced by a transfer drum (intermediary transfer belt) contacted to the photosensitive drum. Another example is uniforming means, contacted to the photosensitive drum and reciprocated in the longitudinal direction, for uniforming untransferred toner on the photosensitive drum.
It is a further object of the present invention to provide a process cartridge, a load producing member and an electrophotographic image forming apparatus to which the process cartridge is detachably mountable in which the torque required for rotating the photosensitive drum is increased by tightening on the peripheral surface of a member rotatable together with the electrophotographic photosensitive drum.
According to an aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said process cartridge comprising an electrophotographic photosensitive drum; process means actable on said electrophotographic photosensitive drum; a load producing member for imparting a load on a peripheral surface of a cylindrical member rotatable with the photosensitive drum to increase a rotational torque required for rotation of said photosensitive drum.
According to another aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said process cartridge comprising an electrophotographic photosensitive drum; process means actable on said electrophotographic photosensitive drum; a load producing member for tightening on a peripheral surface of a cylindrical member rotatable with the photosensitive drum to increase a rotational torque required for rotation of said photosensitive drum; said load producing member including a spring member extended around said peripheral surface for tightening on the peripheral surface of said cylindrical member, a contact portion, provided at one axial end of said load producing member, contacted to a flange which is provided at one end of said photosensitive drum, for rotation of said cylindrical member with said photosensitive drum; a thrust force producing portion, disposed at the other axial end of said load producing member, for imparting to said photosensitive drum a thrust force away from said load producing member in an axial direction of said photosensitive drum.
According to a further aspect of the present invention, there is provided a load producing member for increasing a torque required for rotating an electrophotographic photosensitive drum usable with an electrophotographic image forming apparatus, said load producing member comprising: a cylindrical member having a central through-hole through which a drum shaft of said photosensitive drum is penetratable; a spring member extended around a peripheral surface of said cylindrical member to tighten on the peripheral surface of said cylindrical member; a contact portion, provided that one axial end of said load producing element and contacted to a part of a flange provided at one end of said photosensitive drum, for rotation with said photosensitive drum; and a thrust force producing portion, provided at the other axial end of said load producing member, for imparting a thrust force to said photosensitive drum in an axial direction of said photosensitive drum away from said load producing member by contact to a part of a cartridge frame when said load producing member is mounted to a process cartridge.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
FIG. 1 is a sectional view of an electrophotographic type color image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a sectional view of a developing device used in the color image forming apparatus shown in FIG. 1.
FIG. 3 is a perspective view of an outer appearance of the color image forming apparatus shown in FIG. 1, in which a front cover is opened.
FIG. 4 is a longitudinal sectional view of a process cartridge according to an embodiment of the present invention.
FIG. 5 is a longitudinal sectional view of a toner supply container according to an embodiment of the present invention.
FIG. 6 is a side view of a major portion of the photosensitive drum according to an embodiment of the present invention.
FIG. 7 is a front view of the photosensitive drum shown in FIG. 6.
FIG. 8 is a sectional view of the photosensitive drum shown in FIG. 6.
FIG. 9 is a sectional view of a photosensitive drum which is a modified from that shown in FIG. 8.
FIG. 10 is a sectional view of a photosensitive drum according to another modification in which there is provided a means for stabilization of rotation and thrust direction position.
FIG. 11 is a sectional view of a modified photosensitive drum in which the rotation and the thrust direction position are stabilized.
FIG. 12 is a perspective view of a load producing member according to an embodiment of the present invention.
FIG. 13 is an exploded perspective view of a non-driving side of a photosensitive drum provided with the load producing member according to an embodiment of the present invention.
FIG. 14 is a sectional view of a photosensitive drum according to an embodiment of the present invention.
FIG. 15 is a perspective view of a non-driving side of the photosensitive drum provided with the load producing member according to an embodiment of the present invention.